Three metal surface treatment FAQs
Broadly speaking, metal coatings exist to protect the base metal from corrosion and wear, improving its durability and lifespan. Some also add properties the base metal does not have, such as hardness, electrical insulation or a particular colour. Each treatment has its own strengths, so here are answers to three questions buyers commonly ask.
How do I select the right surface treatment?
Start with what the part has to do and where it will be used. The main factors are the environment it will work in, the standards it must meet, the material it is made from, your budget and your timescale.
- Environment: indoor, outdoor, marine, high temperature or chemical exposure.
- Function: corrosion protection, wear resistance, low friction, appearance or electrical properties.
- Base material: steel, aluminium, titanium, copper alloys or plastics.
- Tolerances: how much thickness the fit can accept.
- Standards: customer, industry and environmental requirements, such as restrictions on certain chemicals.
As an example, anodising and plating are two of the most popular forms of metal surface treatment. While electroplating is a manufacturing process, which deposits a thin layer of metal on a composite or metal substrate, anodising is an electrochemical process that thickens the natural oxide layer on the surface of the metal.
Anodising is mainly used on aluminium, and also on titanium and magnesium. Plating can be applied to a much wider range of materials, which can make it better suited to mixed assemblies or steel parts.
Where can I get tailored advice about surface treatment options?
Some parts benefit from a combination of treatments, such as a plated layer with a sealer or dry film lubricant on top. Some surface treatment providers such as https://www.poeton.co.uk/surface-treatments/, offer bespoke solutions during which their team will work alongside you to create a personalised solution that’s tailored to your specific needs.
To get useful advice quickly, send the provider a drawing, the base material, the quantity, what the part does and what has gone wrong with it before, if anything. The more they know about the working conditions, the better their recommendation will be.
What are the most popular metal surface treatments?
There are many surface treatments, each with its own strengths. Some of the most widely used are anodising, conversion coatings, dry film lubricants and plating.
| Treatment | What it does | Typical materials |
|---|---|---|
| Anodising | Thickens the natural oxide layer for wear and corrosion resistance, can be dyed | Aluminium, titanium, magnesium |
| Conversion coatings | Thin chemical layer that improves corrosion resistance and paint adhesion | Aluminium, zinc, steel |
| Dry film lubricants | Reduce friction and galling without oil or grease | Most metals |
| Plating | Deposits a metal layer, such as nickel, zinc, chrome or silver | Steel, copper alloys, aluminium, some plastics |
Common mistakes when choosing a treatment
- Choosing a finish on appearance alone, without thinking about wear or environment.
- Forgetting that a coating adds thickness, which changes fits and threads.
- Specifying a treatment that does not suit the base material.
- Leaving the choice until the design is finished, when it is harder to change.
Where to go next
For the basics of each process, read our introduction to surface treatments, or see why engineers choose hard anodising for demanding aluminium parts.
